Fixing the touch screen on a Hannspree tablet
I have a Hannspree Android tablet with a 13.3″ screen. I use it to display sheet music when playing the piano. It is a very useful item. The screen is not quite A4 size but is adequate for lead sheets. I would prefer a larger screen with an E-ink display, but the latest offering is in excess of £600. My Hannspree tablet was £200 so I want to get the most out of it as it was purchased primarily for reading sheet music.
Unfortunately as with all consumer items, it has developed a serious fault. One day I discovered that the right hand of the screen was not responding to touch. During the course of the year the dead “column” became progressively wider and is now half the screen. It is becoming a bit difficult to operate. I wanted to fix it.
I wondered about the possible reasons for this failure. It could be a disconnection of a sensor wire to the screen, static damage to the detector, damage to fine wires embedded in the glass or maybe X rays from airport scanners. Tablet screens detect touch by change in capacitance. The sensors are embedded in the top glass that lays over the display and routed by a flexible printed cable to a microcontroller. The high impedance inputs to microcontrollers are susceptible to static damage and this is my number one suspect for the failure.
I have never looked inside a tablet before so i consulted some utube videos on how to take it apart. The tablet has a back panel that is secured by screws and plasticated internal catches. It is fairly easy to dismantle once you get the knack. I needed to fashion a special tool by taking a used credit card and sharpening one side to a knife edge using some sand paper.
There are two micro screws on the edge that houses all the electrical sockets. I used a spectacle screwdriver to remove these. If you look closely at the sockets you can see a hairline where the back panel joins the main body. You need to judiciously slide the plastic knife edge of the tool into this gap to lever the panel away. The internal catches are released when the knife edge slides passed them. You should not insert the tool too far in. Slide the tool all the way around the tablet edge to get the entire panel off. Note that the panel simply clicks back with a small amount of pressure around the edges.
Watch out for the plastic power button thats falls away.
Also remove an SD card if fitted before starting.
The photo shows the insides once the panel has been removed. The battery is mid centre and is soldered with two wires to the processor board on the right. This would be an easy item to replace. The cables are simply taped down with stcky tape.
The brown connector cable with micro-controller at the top right corner is the interface to the touch screen. The plastic printed cable is joined to the main processor board using a pinch connector. These have a plastic bar along the top. You lift the bar up using a fingernail to release the cable and the cable can be pulled out.
The next photo shows the touch screen controller in more detail. The controller connects to the touch screen using the top printed flexible cable and connects to the main processor board with the bottom printed flexible cable. The controller measures the touch sensor capcitance, sorts out the position information and communicates using a (SPI) serial bus. This is the beast that needs replacing.
I looked up the code numbers F-WGJi3308-V1 ILI2303 M1447 printed in white at the top on the Ali-Express website and got the following :-
Ali-Express is a chinese website that sources just about everything. I ordered the part for $40 and started to wait……………………………………………… and wait………………………………….
The replacement part arrived after a month and a day. It was well packed and in tact when I unwrapped it carefully. The replacement part is the entire touch screen glass, microcontroller and flexible cables assembly together with some double sided adhesive strips. It has two protective plastic films each side.
I took the back off the tablet and disconnected the old touch sensitve screen and connected the new one in its place. I then powered up and checked that the new screen was functional. I then disconnected it.
The touch sensitive screen is attached to the plastic frame using double sided adhesive tape. The hard bit is to persuade the screen to leave the plastic frame. I wanted to remove the glass panel in tact but it cracked halfway through. It is probably best to crack the screen in the first place.
However I gently prised the screen using a sharp knife at one corner and inserted a blade of tough, thin plastic between the frame and the glass. I then pulled and pushed it to release the glass. Once I had got a sizeable gap, I use a sharp knife to prise the glass away from the frame. I wore glasses during this in case the glass shattered and projected splinters into my eyes.
There are two loudspeaker grills that are held by the glass. These come loose and I stowed them safely away.
Most of the adhesive tape was attached to glass which I dumped. I used lighter fluid and tissue to clean residual parts of adhesive from the frame, as shown above. Note that the gap at the bottom right is to allow clearance to push the cable and micro-controller through.
I then cut the new adhesive strips to size and stuck them on the frame. The uppermost side is left covered by the backing paper. Note that a hole is needed where the camera is and the slot for cables needs to be uncovered.
The speaker grilles were then placed in position.
I then placed the new glass screen in position and checked that the cables could be threaded through OK and that it fitted the frame nicely. It was a good fit so I proceeded to do the sticking down.
It is a bit fiddly to manoeuvre the screen into position, so I partially uncovered the adhesive tape and bent the backing tape so that I could extract it with the glass more-or-less in position.
Before sticking down, I cleaned the LCD screen using a rag and methylated spirit. I also put the grilles in position and removed the glass protective film. Note that there are no second tries at doing this so everything must be right first time !!!
I positioned the screen,threaded the cable and micro-controller, pulled out the backing tapes and carefully set the glass into the frame at the edges. This went really smoothly.
I then turned the tablet over and re-connected the ribbon cable to the processor card. I then put the back panel on the tablet and snapped it into place.
I powered on and the tablet was fixed !!!
I was really chuffed about this and this was £31 well spent. I had previously contacted Hannspree about getting it fixed and received NO REPLY from the toe-rags. I estimate that the time spent to fix this is about an hour so an honest repairer would probably charge about £80 to do the entire job including parts. I say honest as there are some toe-rags out there that would invent other things to fix and charge extra.
The tablet cost £200 so any repairs over £100 are probably not economic, such is our throwaway society but I think this repair was worth it. I now feel confident enough to repair mobile phones that have cracked screens.